1. Field of the Invention
The invention relates to a membrane electrode assembly used in a fuel cell.
2. Description of the Related Art
A fuel cell is comprised of a plurality of unit cells that are stacked together, and each unit cell has a membrane electrode assembly sandwiched by and between separators. The membrane electrode assembly consists of an electrolyte membrane, and a pair of electrode catalyst layers by and between which the electrolyte membrane is sandwiched. Manifold holes that provide fluid channels for, for example, fuel gas and water are formed in an outer peripheral portion of the membrane electrode assembly. Also, in order to improve the fluid tightness of the membrane electrode assembly sandwiched between the separators, a technique for forming a seal gasket by injection molding on the opposite surfaces of the membrane electrode assembly is known (as disclosed in, for example, JP-A-2003-68319).
However, problems are likely to occur in the process of manufacturing the membrane electrode assembly since its constituent components, such as the electrolyte membrane and the electrode catalyst layers, have low strength. For example, when the membrane electrode assembly is placed in a mold for injection molding of the seal gasket, a portion of the membrane electrode assembly which is not supported in a cavity of the mold may be warped or curved under the influence of, for example, the gravity. If a seal material that is in a fused state is injected into the mold in this condition, flow of the seal material may be hampered or obstructed, resulting in occurrence of molding failures or defects.
Also, the membrane electrode assembly has another problem that its constituent components are likely to peel off from outer end faces of the assembly.